Surge filter for pulsating gases



Feb. 6, 1940. R a., LEADBETTER' 2,189,425

SURGE FILTER FOR PULSATING GASES Filed Oct. 24, 1938 2 perforatedimpedance member 2, the latter being in alignment with inlet conduit 3and, optionally, round or oval in cross section. A tail pipe '4 connectswith by-pass chamber 4a. The only entrance into chamber I is viaimpedance member 2. The area of gap b between contiguous ends of conduit3 and member 2, that is, the area of the surface generated by drawinglines from points on the periphery of the inner end of conduit 3 to thenearest points of the periphery of the mouth of member 2, should not besubstantially less than the cross-sectional area of inlet conduit 8.-Restated, and oy Way of example, if conduit member 3 andimpedance member2 are circular in transverse section and have the same diameters, bshould not be substantially less than one-fourth a. With thisrelationship it will be seen that a substantially unrestrictedpassageway is provided through which the gases may `flow, as indicatedby the arrows, without entering snubber chamber I. This 'unrestrictedpassageway is the shunt path referred to above.

In the operation loi the device, the gas slugs are projected throughinlet conduit 3 toward snubber chamber I. The path of least resistancewould be from the inlet conduit directly to outlet conduit 4 throughby-pass chamber la, but

- a portion of each slug has sulcient inertia imparted by the extremelyhigh pressure conditions within the cylinder of the exigirle at themoment the exhaustv'alve opens to cause that portion of the slug toenter snubber chamber I via perfol rated member 2. The velocity energyof the slug is transformed into static pressure within impedance member2 as the slug is brought to a cushioned stop, the pressure beingdissipated by v an expansion ci. the gases into thespace of chamifrom,chamber I., resulting, rather, in a relatively gradual introduction ofgases into the chamber and a relatively gradual restoration of the gasesfrom this chamber to the by-pass chamber 2. A snubber effect is therebyobtained which reduces the gas-velocity-peaks of the flowing gaseswhereas a chamber without the impedance means described would merelyreflect and possibly aggravate the pulsations. Additionally, it may benoted that the time lag caused by the impedance and the cooling (andtherefore contraction) of the expanding gases materiallyV aid thesnubbing operation in reducing the magnitude of the velocity peaks.

No representation is made that the device above described is alonecapable of preventing f or attenuating pulsating gas noises to a degreeconsidered satisfactory to the art except in certain cases.Thisdatcibeis-emoient in the smoothing of the gas fiow and therefore inthe removal of ythe cause of noise. In particular, sounds in the lowerfrequency ranges are prevented by virtue of the invention. However, thedevice is intended" to be used in conjunction with means forattenuatingl the high frequency sounds. A simple expansion chamber or apacked muii'ier constructed in'accordance with the disclosure of SchnellPatent No. 1,811,762, dated June 23, 1931,

may be used for this purpose. Such a unit may be connected either inconduit 3y or in conduit 4.

A construction in which the snubbing unit above described is combinedwith a simple expansion chamber is shown in Figs. 2 and 3. A cylindricalshell 5 is provided with end flanges 6 and 'l having inlet opening 3 andoutlet opening 9 therein, respectively. Inlet snout Il! is mounted inend iiange B at inlet opening 8 and exhaust snout Il is mounted atopening 9 in end fiange 1. A partition I2 having an openingA I3 thereinin alignment with inlet opening 8 and an opening I4 not in alignmentwith inlet opening 8 is arranged transversely Within shell 5 in spacedrelation to inlet end flanged to form by-pass chamber i5. A shell I6,including closure member. Il. denes snubber chamber I3 into which animpedance means in the form of a perforated. closed-ended tube Itprojects. The latter opens into by-pass chamber I5 at opening I3.snubber chamber I8 is entirely closed so that gases vmay enter it onlyvia opening I3 and perforations 2K6. The gases must leave this chamberby the same path. Perforated conduit 2I connects Icy-pass chamber I5with theoutlet open- The ing 3 and may be integral with exhaust snoutIl, as shown. The perforations in the walls of conduit 2i permitexpansion of the gases traveling through the conduit into space 22. l

The operation of the snubbing unit of the device of Figs. 2 and 3 is asabove described. The high velocity portion of a slug entering the devicethrough inlet snout III jumps the gap c and is snubbed in the snubbingchamber I6. The remainder of the gases by-pass from opening 8 directlyto conduit 2l and are exhausted to the atmosphere. The gases enteringinto and operated upon by the snubbing unit are gradually restored toby-pass chamber I5 whence they flow through conduit 2i to theatmosphere. Expansion chamber 22 cooperates with the snubber unit inremoving or preventing substantially all of the noises which wouldotherwise becaused by the pulsating gases.

VGap c should be suiiiciently large to permit substantially unrestrictedilow of gases through the device via openings 8, Il and 9. While-thedegree of perforation of impedance members I9 and 2 (Fig. 1) is notcritical, they should be sufficiently open to permit the proper degreeof expansion of the gases entering them into the surrounding space.result in the loss of the necessary impedance to the flow. of gases intothe snubber chamber andv the reflection of pulsations therefrom.Empirical yfindings indicate that the impedance member should beperforated suiciently to provide atotal open area of 5 per cent of, to 4times, the crosssectlonal area of the inlet snout or exhaust pipeleading to the muliler. The snubber chamber itself should besufcientlylarge to permit substantial expansion of the gases into itfrom the impedance member.

. Without limiting the invention and by way of example it is noted thata mufller constructed substantially as shown in Figs. 2 and 3 and havingthe following dimensions operated satisfactorily in preventing exhaustnoise from a single cylinder, four cycle internal combustion gasolineengine of 2-horse-power at 1800 revolutions per Excessive perforationwould i minute having a cylinder bore of 2% inches and stroke of 2%inches: shell 19 inches long by 4 inches in diameter, gap c 11/2 inches,impedance member 16 inches long by 1 inch in diameter and perforatedsuiciently to provide walls 4 per cent open, diameter of snubber chamber2%' inches.

This invention is adaptable to embodiment in various forms notspecifically shown or described herein but following the principlesthereof. For example, inner shell IS may be concentric with perforatedconduit 2| thus providing a snubber chamber occupying the entire volumeof outer shell 5 except that enclosed by the imperforate inner shell.The term perforated is intended to cover all equivalent constructionswherein the member may be apertured otherwise than by stamping out smallround portions of the material. Although the impedance means isillustrated as elongated and tubular, it is clear that this member maytake other suitable forms. 'Ihe invention is limited only by the scopeof the appended claims.

I claim:

l. In a device of the character described, gasvelocity-peak snubbingmeans comprising means forming a snubber chamber having substantiallyimpervious walls, means forming a by-pass chamber, gas-flow impedancemeans arranged within said snubber chamber and having an entranceexteriorly thereof opening into said` by-pass chamber, a conduitextending toward said impedance means entrance for conducting pulsatinggases toward said entrance, said conduit terminating short of saidimpedance means entrance within said by-pass chamber, and means foregress of gases from said by-pass chamber.

2. A device in accordance with claim l in which said conduit terminatesshort of said impedance means entrance by such a distance'that the areaof the gap between the entrance to said impedance means and thecontiguous end of said conduit is not substantially less than thecrosssectional area of said conduit.

3. In a device of the character described. gasvelocitypeaksnubbing meanscomprising a shell having an opening in a wall thereof, .a transversepartition within said shell dividing the volume thereof into a snubberchamber and a by-pass chamber, said partition having an opening thereinin alignment with said shell wall opening, gas-flow impedance meanswithin said snubber chamber having an entrance at saidl chamber from theperiphery of said opening in said partition the end of said tube withinsaid snubber chamber being substantially closed, an inlet conduitextending through said shell wall opening and terminating in saidby-pass chamber short of said perforated tube entrance, and an exhaustconduit connecting said by-pass chamber with the atmosphere.

5. In a device of the character described, a cylindrical shell havingend closures and a transverse partition therewithin, a concentricopening in an end closure and a concentric opening in said partition,impedance means having an entrance at said opening in said partition andextending intothe space within said shell away from said end closurehaving an opening therein, a conduit'connecting with a source ofpulsating, flowing gases and `extending through said opening in said endclosure, said conduit terminating short of said impedance meansentrance, and f an exhaust conduit connecting the space between saidpartition and said end closure having an opening therein with theatmosphere.

6. In a device of the character described, an outer shell having inletand outlet end closures having inlet and outlet openings therein,respectively, a transverse partition arranged within said outer shell inspaced relation with said inlet end closure to form a by-pass chamberand having an opening therein in alignment with said inlet opening, aninner shell dividing the space within said outer shell and between saidpartition and said outlet end closure into a snubber chambercommunicating with said by-pass chamber by means of said opening in saidpartition and an expansion chamber, a tubular member having perforatedwalls within said snubber chamber opening into said by-pass chamber atsaid opening in said partitionv the opposite end being substantiallyclosed, and 'a perforated conduit passing through said expan,

a opening therein away from said inlet opening,

the end of said tubular member remote from said partition being coveredby a perforated closure member, an inner shell surrounding saidperforated tubular member and providing a space between said tubularmember and said inner shell, and a perforated conduit within said outershell and without said inner shell connecting said by-pass chamber withsaid outlet opening.

RALPH L. IEADBEI'IER.

